Incandescent electric lamp



(No Model.)

' T. A. EDISON.

INOANDESOENT ELECTRIC LAMP.

N 534,g0 Patented Feb. 12, 1895.

666 or Z1770.

Copper.

wAsHma'ron n c UNITED STATES PATENT OFFICE.

- THOMAS A. EDISON, OF LLEWELLYN PARK, NEW JERSEY.

INCANDESCENT ELECTRIC LAMP.

SPECIFICATION formingpart of Letters Patent No. 534,209, dated February 12, 1 895. Application filed September 17,1890. Serial No. 365,260. (No model.)

T0 at whom it may concern.-

Be it known that I, Tn'roMAs A. EDISON, a citizen of the United States, residing at Llewellyn Park, in the county of Essex and State of New Jersey, have invented a certain new erto been the only metal used for this purpose because its coefficient of expansion when heated is practically the same as that of glass. I have found, however, that an efiective seal can be obtained by the use as a leading-in wire of a compound wire whose outer portion is composed of a readily fusible metal such as tin, zinc or lead, or alloys of which such metals are the principal ingredients, this being placed upon an inner base or core of a metal having a comparatively high fusing point, such as copper, silver, nickel, cobalt,

venient to handle in the operation of fusing iron or steel. Of these metals I prefer copper because this metal gives off scarcely any air or occluded gases when heated, and because its fusing point is so high as to make it conthe glass upon the wires. For the outercovering or envelope I prefer tin.

In putting said invention into practice I take pieces of the compound wire described, of sufficient length and lay them within the glass tube which is to form the inner stem or wire support, and I seal such wires in the end of the tube-with their ends projecting therefrom-in the usual manner, that is to say, the glass is melted by a blow -pipe flame and is 7 then pinched or pressed down upon the wires by means of a suitable tool, so that a solid flat Y end is produced .on the tube in which the wires are held in a fixed position. At the moment'of sealing, the wires should be quickly drawn forward a short distance so as to bring a fresh and cooler portion of them into the seal. Since the specific heat of the fusible metal is very low, it sets instantly when the seal'is made, so that an intimate union is pound wire gives the necessary mechanical strength to the structure.

The wires are attached to the filament or incandescent conductor and the glass tube or stem is inserted in the globe and sealed therein in the usual or any suitable manner.

The compound wires may be formed in any effective wayfor instance, by drawing the copper wire through a bath of melted tin or other metal which adheres to its surface; the whole being then drawn through a die plate to remove the superfluous metal. The proportion in size of the two metals maybe, for a copper wire twelve one-thousandths of an inch in diameter a coating 'of fusible metal two one-thousandths thick.

In the accompanying drawings, Figure 1 is aview in elevation of an incandescent electric lamp embodying my invention; and Fig. 2 an enlarged cross-section of one of the leading-in wires.

A is the globe, B the inner stem, and O the flattened seal through which the leading-in wires pass to the incandescent conductor D, such wires being each composed of a central core of copper or other wire of high fusing point, and anouter covering of tin, lead, zinc or equivalent metal or alloy.

What I claim isr In an incandescent electric lamp, the combination with the glass stemlor wire support of leadingdn wires passing through the same and held therein by the fusing of the glass tube upon them and each composed of an outer covering of readily fusible metal or alloy and an inner core or base of metal of comparatively high fusing point, substantially as set forth.

This specification signed and 13th day of September, 1890. V

THOS. A. EDISON.

witnessed this Witnesses: 4

W. PELZER, RICHD. N. DYER. 

